Wide-Dynamic Range Electrometer with a Fast Response
First Claim
1. An electrometer, comprising:
- an amplifier having an inverting input, a non-inverting input, and an output;
first and second resistive elements each having a first end and a second end, the first ends of the first and second resistive elements electrically coupled to the inverting input of the amplifier and the second end of the first resistive element electrically coupled to the output of the amplifier;
a buffer having a high-impedance input and an output, the second end of the second resistive element electrically coupled to the input of the buffer; and
at least one diode electrically coupling the output of the amplifier to the second end of the second resistive element.
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Abstract
A method and apparatus for measuring current includes sensing a first voltage at the output of an amplifier and computing a current based on the first voltage and the resistance of a first resistive element, which is electrically coupled between an inverting input of the amplifier and the output of the amplifier, if the first voltage is below a predetermined level. The method also includes sensing a second voltage at the output of a buffer and computing a current based on the first and second voltages and the resistances of the first resistive element and a second resistive element, which is electrically coupled between the inverting input of the amplifier and an input of the buffer and is also electrically coupled to the output of the amplifier through a at least one diode, if the voltage output from the amplifier is above the predetermined level.
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Citations
19 Claims
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1. An electrometer, comprising:
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an amplifier having an inverting input, a non-inverting input, and an output; first and second resistive elements each having a first end and a second end, the first ends of the first and second resistive elements electrically coupled to the inverting input of the amplifier and the second end of the first resistive element electrically coupled to the output of the amplifier; a buffer having a high-impedance input and an output, the second end of the second resistive element electrically coupled to the input of the buffer; and at least one diode electrically coupling the output of the amplifier to the second end of the second resistive element. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. A method for measuring current, comprising:
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sensing a first voltage at the output of an amplifier; computing a current based on the first voltage and the resistance of a first resistive element electrically coupled between an inverting input of the amplifier and the output of the amplifier if the first voltage is below a predetermined level; and sensing a second voltage at the output of a buffer; computing a current based on the first and second voltages and the resistances of the first resistive element and a second resistive element, the second resistive element being electrically coupled between the inverting input of the amplifier and an input of the buffer, if the voltage output from the amplifier is above the predetermined level. - View Dependent Claims (15, 16, 17, 18, 19)
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Specification